Medical sewage mainly refers to sewage discharged from different hospital units such as outpatient treatment room, testing laboratory, ward (including laminar-flow clean ward), laundry room, dressing change room, injection room, ICU room, X-ray room, burn ward, operating room (including laminar-flow clean operating room), blood bank, experiment laboratory, infectious disease treatment area, protective isolation ward, sterile supply room, hospital toilet or laundry room. The sources and components of the sewage are very complex, and the sewage contains a large number of pathogenic bacteria, viruses and chemical agents, such as drugs, disinfectants, diagnostic agents, detergents, as well as a large number of pathogenic microorganisms, parasite eggs and various viruses, such as ascaris eggs, hepatitis virus, tubercle bacillus and dysentery bacteria, thus having the characteristics of space pollution, acute infection and latent infection (Qu Jijun, He Zheng, Lin Yaokun. Investigation on Sterilization of Medical Sewage in Some Hospitals in Guangzhou [J]. Chinese Journal of Public Health Management, 2010, 26 (3): 298-299). In particular, bacteria, viruses and parasite eggs in hospital sewage have certain resistance in the environment, some of which live in sewage for a long time. When people eat or come into contact with water or vegetables contaminated by bacteria, viruses, parasite eggs and toxic and harmful substances, they will cause diseases or cause outbreaks of infectious diseases. Through epidemiological investigation and bacteriological examination, it has been proved that all previous outbreaks of large-scale infectious diseases in China are related to drinking or contacting contaminated water. For example, a large-scale outbreak of hepatitis A occurred in Shanghai in 1988, which was caused by contamination of clams by dung boats carrying hepatitis A virus (Ye Wanfang, Cai Tongzhang. CLINICAL COURSE AND PROGNOSIS OF VIRAL HEPATITIS IN A 1988 SHANGHAI EPIDEMIC—A FIVE YEARS FOLLOW-UP STUDY OF 1075 CASES . . . [J]. Shanghai Medical Science, 1993, 16 (11): 629-632) In recent years, cholera has occurred in many countries in the world, with a wide outbreak area and a large number of deaths, which is rare in history, and most of the cases have occurred in coastal areas of underdeveloped countries. It is reported that all these cases are due to the fact that the drinking water is contaminated by excrement of patients. Compared with industrial waste water and domestic waste water, the medical sewage has the characteristics of small amount and strong pollution. If the medical sewage is allowed to be discharged, it will seriously pollute water sources and spread diseases.
According to the data of the International Bureau of Statistics of China in 2009, the national discharge of medical sewage was 446.548 million tons, but the qualified discharge was only 388.602 million tons, with a compliance rate of 87.0%. The discharge of COD in medical sewage amounted to 702.749 million tons, and the discharge of ammonia nitrogen amounted to 73.528 million tons. Data of Guangdong Province in the same year showed that the medical sewage discharge was 45.595 million tons, but the qualified discharge was only 37.039 million tons, with a compliance rate of only 81.23%, which is significantly lower than the national average compliance rate. The alarming data warns that the safety and qualified discharge of medical sewage in Guangdong province and even the whole country still has a long way to go. Because it is related to life safety, environmental safety or public health, China is cautious about medical sewage discharge and increasingly strict in management, which also puts forward higher requirements for medical sewage sterilization technology.
The existing medical sewage treatment technologies are of varying quality. Some enterprises have only made some improvements on the traditional industrial sewage treatment technology by adding sterilization procedures, such as adding ultraviolet disinfection, hydrogen peroxide or ozone disinfection technology, etc. (Li Jian. Study on Disinfection treatment and Practical Application of Hospital wastewater containing bacteria [D]. Jilin University, 2011). Some organizations have explored the medical sewage sterilization process of “hydrolytic acidification+biological contact oxidation+disinfection” (Liu Xi. Hospital Wastewater Treatment with the Hydrolysis Oxidization Technology [J]. Journal of Environment and Health, 2005, 22 (3): 209-211). There are also researchers who have come up with such a design that a closed water collection tank, a closed primary sedimentation tank, a closed sludge tank, a closed sludge disinfection tank, a closed sewage sterilization tank, a coagulation tank, a coagulation sedimentation tank, a biological filter tower and a secondary sedimentation tank which are connected in sequence for medical sewage treatment (Dong Yubo. Medical Wastewater Purification Recovery Treatment System Mainly Based on Flocculation and Biologic Filter. ZL 101591096). Xu Weiqi et al., have developed a treatment agent for medical sewage, including titanium dioxide 20-200, silicon dioxide 40-300, zinc acetate 40-120, etc., and used it in disinfection and evaporation of medical sewage (Xu Weiqi. Treatment Agent for Medical Sewage and Method for Odorless Treatment of Medical Sewage. ZL 201711088979.2). Shao Chunyan et al., have developed a self-control disinfection device for medical wastewater, which is characterized in that a water injection opening is formed in the top of an upper-layer medicine dissolving box and a medicine feeding opening is formed in the upper part of the medicine dissolving box; an emptying opening is formed in the lower part of the medicine dissolving box and a stirring pump is mounted in the medicine dissolving box; an electric control part of disinfection equipment and a medicine feeding pump are mounted in an electric control cabinet; a medicine suction pipe of the medicine feeding pump is communicated with the medicine dissolving box; a medicine discharging pipe of the medicine feeding pump is communicated with a disinfection box; a high-liquid-level automatic valve is arranged at the upper part of the medicine dissolving box; a low-liquid-level automatic valve is arranged at the lower part of the medicine dissolving box; a sewage water inlet and a processed-water water outlet are formed in the upper part of a lower-layer disinfection box; an emptying opening is formed in the bottom of the disinfection box. (Shao Chunyan, Chen Shourong, Wu Di, Wang Hongning, Jiang Haichang. Self-control Disinfection Device for Medical Wastewater. ZL 201711161454.7).
However, it is worth noting that the existing traditional medical sewage sterilization process still faces the problem of incomplete sterilization, for example, some pathogenic bacteria, including common bacteria, viruses, spirochetes, rickettsia, chlamydia, mycoplasma, fungi and actinomycetes still remain (Lu Xuekui, Hua Yijiang, Jia Qiufang. Investigation on Disinfection Effect of Medical Sewage [J]. Chinese Journal of Disinfection, 2007, 24 (1): 88-88). If the medical sewage that is not thoroughly treated and fails to meet the standard is still discharged to the outside, it will easily cause public health incidents and the social impact will be unprecedented. The market also calls for a new medical sewage sterilization technology and related devices that are thorough and efficient in medical sewage sterilization and simple and inexpensive.